Networking

Info 253: Web Architecture
Kay Ashaolu

The Web Is Built On The Internet

We Use These Phrases

  • "Connects to server"
  • "Sends response to client"
  • "Closes the connection"

What do they mean?

Internet Architecture is Composable

  • Emphasize flexibility
  • Allow for growth, incremental adoption
  • Interchangeable parts

Two Computers Need to Communicate

  • String a wire between them
  • Send bits across via voltage changes
  • Wait for response?

Three Computers Need to Communicate

Get more wire

Circuit Switching

  • New computer joins network: wire it up
  • Switch the electronic circuit

Network

  • Now we have a network
  • Mostly computer-to-computer
  • How do we communicate between networks?

ARPANET :: Network

  • Circuit Switching -> Packet Switching
  • Relied on Interface Message Processors (IMPs)
  • Government, no commercial traffic

Packet Switching

  • Send small packets of information
  • Addressed to a receiver
  • Can share medium

Internet Protocol

  • Moves responsibility to host software
  • Keeps packet switching and routing
  • Adds concept of ports

Internet Protocol

  • Where is the destination? (host addressing)
  • How do I get there? (routing)
  • Stateless!

Packets travel over networks

  • Packets sent from my house to the iSchool's servers
  • Destination is specified with a number (IP address)
  • Routing is done by forwarding to the next best network

Traceroute

sudo apt-get install traceroute
traceroute ischool.berkeley.edu

traceroute to ischool.berkeley.edu (128.32.78.26), 30 hops max, 60 byte packets
 1  10.0.2.2 (10.0.2.2)  0.544 ms  0.293 ms  0.129 ms
 2  192.168.0.1 (192.168.0.1)  3.254 ms  3.170 ms  3.162 ms
 3  homeportal (192.168.1.254)  8.748 ms  8.729 ms  8.696 ms
 4  107-193-136-2.lightspeed.sntcca.sbcglobal.net (107.193.136.2)  
 	37.250 ms  39.226 ms  39.162 ms
...
 13  t2-3.inr-201-sut.berkeley.edu (128.32.0.37)  
 	68.950 ms  71.289 ms t2-3.inr-202-reccev.berkeley.edu (128.32.0.39)  71.450 ms
 14  et3-47.inr-311-ewdc.berkeley.edu (128.32.0.103)  
 	71.227 ms  71.380 ms et3-48.inr-311-ewdc.berkeley.edu (128.32.0.101)  71.448 ms
...

IP Address

  • Numbers, often represented as "dotted decimal" (199.255.189.160)
  • But can also be represented as just a number (3355426208)
  • IPs assigned by Internet Assigned Numbers Authority

Routing

  • Border Gateway Protocol tracks routes to IPs
  • ISPs manually configure peers to share information
  • Routers use BGP to forward packets

Ethernet

  • All computers on the same physical medium
  • "Frames" addressed to a receiver

Questions